The iPhone 4 came in two GSM, 8gb versions. There's no way of knowing which version this is. The first was 6/24/10 - 10/14/11. The revised model 10/4/11 - 9/10/13. Even if these are "new", how would the battery behave after sitting dormant for at least 3 years?

Agreed with Brook. Most apps now require at least iOS 8, and either can't even be downloaded from the App Store or the app developers ended support for iOS 7 or lower (iPhone 4 only goes up to iOS 7). Even with iOS 8, many apps have now completely lost support (Discover, American Express, Snapchat, etc.). These days you need at least iOS 9 or above if you expect to be using an iPhone.